The present invention relates generally to UV fluid treatment systems and specifically to such systems and methods that incorporate electrodes to facilitate advanced oxidation processes (AOP). Such electrodes include those that are based on electrolytic production of hydrogen peroxide, or are optimized for the production of hydrogen peroxide and/or for the destruction of organic contaminants in industrial wastewater, including mixed metal oxide electrodes having two kinds of metal oxides, such as those disclosed in U.S. Pat. No. 8,580,091 (issued Nov. 12, 2013), included herein by reference as if fully re-written herein.
AOP that generally use UV plus peroxide can be used for many water and wastewater (i.e. fluid) based oxidation processes. Conventional peroxide systems are chemical based and generally require the dangerous chemical to be tankered in and stored. The present invention offers many advantages over what is done now.
In one embodiment, the present invention incorporates an L-shaped electrode, placed upstream from the UV lamps, that forms hydroxyl radicals. The electrode is inserted into the UV reactor through the existing access hatch.
In one embodiment, elongated, tubular UV lamps are used as the UV radiation source. Such lamps produce the least UV at their ends. In other words, the radiation intensity is diminished resulting in a lower UV dosage delivered near the lamp ends.
Additionally, elongated medium pressure (MP) lamps blacken over time and the arc shortens. These characteristics result in diminished UV dosages in UV reactors having such lamps oriented transversely to the fluid flow. Accordingly, it would be advantageous to direct the flow of fluid away from the ends and towards the center of such elongated lamps. It is also advantageous to move the fluid away from the top and bottom of the chamber (i.e. vertically). The present invention overcomes these, as well as other disadvantageous that will be apparent to those of skill in the art, by tapering the electrode veins so as to direct the flow of fluid towards the center of the elongated lamps—the area of highest UV fluence.
In one embodiment, the electrodes are titanium mesh, coated with Iridium and/or Ruthenium. In one embodiment, the electrodes are made from a mesh-like structure which increases surface area and disrupts the fluid flow pattern more than a solid sheet would; which is advantageous. In one embodiment, the present invention incorporates an electrode inserted into an access hatch of a UV reactor, immediately upstream of the UV radiation source.
By applying a voltage to the electrode the water is hydrolyzed and hydroxyl radicals are formed immediately before the UV system lamps (aka UV radiation source). When the hydroxyl radicals interact with the UV lamps an advanced oxidation process occurs. This process can be used to oxidize many contaminants out of many different types of water, swimming pool, or other recreational water and waste water; including water for reuse, as well as ultra-pure water.
When such a system is operated with the electrode in front (i.e. upstream) of the UV system, it acts as an advanced oxidation process. When the system is operated with the electrode behind (i.e. downstream) the UV lamp, and salt is introduced into the water upstream of the UV lamps, the system will provide a self-contained UV system plus residual chlorine provider.
One advantage of the L-shaped electrode of the present invention is to maximize surface area. The electrode is powered by DC voltage, and it has variable output base on the amperage and DC voltage that is fed to it. The DC voltage can switch, so as to assist in the removal of any scale of hardness from the electrode surface. In one embodiment, the voltage polarity (relative to the cathode and anode) is switched so as to assist in the removal of any scale of hardness from the electrode surface.H2O2+hν→2.OHΦ=1.0
A reduction reaction takes place at the negatively charged cathode with electrons (e−) from the cathode being given to hydrogen cations to form hydrogen gas (the half reaction balanced with acid):
Reduction at Cathode:2H+(aq)+2e−→H2(g)
An oxidation reaction occurs at the positively charged anode, generating oxygen gas and giving electrons to the anode to complete the circuit:
Anode (Oxidation):2H2O(l)→O2(g)+4H+(aq)+4e−
The same half reactions can also be balanced with base as listed below. Not all half reactions must be balanced with acid or base. Many do, like the oxidation or reduction of water listed here.
Cathode (Reduction):2H2O(l)+2e−→H2(g)+2OH−(aq)
Anode (Oxidation):4OH−(aq)→O2(g)+2H2O(l)+4e−
Combining either half reaction pair yields the same overall decomposition of water into oxygen and hydrogen:
Overall Reaction:2H2O(l)→2H2(g)+O2(g)
The number of hydrogen molecules produced is thus twice the number of oxygen molecules. Assuming equal temperature and pressure for both gases, the produced hydrogen gas has therefore twice the volume of the produced oxygen gas. The number of electrons pushed through the water is twice the number of generated hydrogen molecules and four times the number of generated oxygen molecules. Some of the other advantages of the present invention include:
Production of active substances, immediately adjacent to the UV lamp(s) with no harmful disinfection by products;
Elimination of transport, storage, handling of Hydrogen Peroxide inherent with conventional systems;
Scalable, no moving parts; and
The L-shaped electrode improves water flow patterns, which therefore improve the performance of the UV system.
Initiation:H2O2/HO2−=hν→2HO.
Propagation:H2O2/HO2−+HO.→H2O/OH−+HO2.H2O2+HO2./O2.→HO.+H2O/OH−+O2 
Termination:HO.+HO.→H2O2 HO.+HO2500/O2→H2O/OH−+O2 HO2.+HO2500/O2→H2O2/HO2−+O2 